An abstract, presented at the annual gathering of the European Geosciences Union (EGU) in Vienna this week, has caused quite a stir: it concludes that glacial retreat atop volcanoes can trigger landslides that destabilize underlying magma chambers, possibly triggering an eruption.
This has caused some to propose that, if runaway climate change continues to eat away at glacier-topped volcanoes, then we’re likely to experience an uptick in eruptions in various parts of the world. So will it?
Well, not necessarily. First, let’s take a look at what the abstract – not a peer-reviewed paper just yet, so it’s naturally light on details – says.
The research focuses on Mount Meager, a relatively young stratovolcanic complex in Canada. It has a colorful eruption history, with one major paroxysm around 2,340 years ago, which produced the largest known eruption in Canada’s recent history.
It’s currently covered in ice. The more ice you have, the more pressure you’ve got on the magma system below, and this extra pressure can keep the dissolved gases in the magma from turning into bubbles. An uncontrollable decompression event can trigger runaway bubble formation, which leads to a rapid uptick in the internal pressure of the magma.
If this ice melts, then the volcano becomes somewhat unloaded. This can reduce the pressure on the magma source, which could perhaps trigger an eruption. Indeed, this link has been previously theorized in several pre-existing studies for other volcanic complexes, particularly for those covered in plenty of thick ice over a large area.
This abstract adds to this discussion by bringing in landslides. Meager often experiences landslides that are dangerous to human life and infrastructure, but it turns out that this removal of mass may affect the magma source too. If a glacier melts away, and it triggers a landslide, so much mass is removed that it has the potential to trigger a runaway bubble nucleation event and an eruption.
Mathematical modeling by the team suggests the plausible, sudden mass removal atop Meager would induce pressure changes down to a depth of 6 kilometers (3.7 miles), enough to catastrophically disturb the magma chamber that exists around that depth. This could cause a magmatic eruption, or a hydrothermal blast that triggers rapidly moving muddy landslides named lahars.
Importantly, here’s what the abstract doesn’t say. It doesn’t suggest that what has been concluded about this specific volcano applies to other volcanic systems around the world, so we can’t really generalize. Volcanoes all have unique loads and idiosyncratic magma chambers – Meager isn’t representative of them all, not by a long shot.
“In order for a volcanic eruption to be triggered by a decrease in load… the magma chamber also needs to be ready to erupt,” Alison Graettinger, Assistant Professor of Geosciences at the University of Missouri, points out. “This means that decreasing ice volumes due to climate change will not cause volcanoes to erupt that were not close to eruption anyway.”
The research’s lead author Gioachino Roberti, a graduate geoscience student at the University of Clermont-Auvergne (UCA), told IFLScience that some comparisons are possible, though.
“Yes, other volcanic systems may be affected by similar phenomena. There are many glaciated volcanoes in South America, Alaska, Kamchatka, Iceland,” he added. “Other authors showed increased volcanism at the end of the last glacial maximum and now, it may happen at a smaller scale.”
However, Dr David McGarvie, Senior Lecturer in Volcanology at The Open University, said that the evidence for ice unloading-triggered eruptions is strongest in Iceland, but “at best, these studies weakly support this hypothesis, and there are equally valid (but more boring) alternative explanations.”
So what’s the takeaway message here? At present, we can’t simply say if a warmer climate will lead to more volcanic eruptions, and the evidence so far is decidedly mixed.